The increase in May would be the sixth straight in the index, the government's broadest gauge of the costs of goods and services. Economists attributed it to surging gasoline prices and rising consumer demand, which allowed some companies to raise prices.

"Consumer inflation has accelerated so far this year, raising concern that inflationary momentum will prompt the Fed to raise rates more aggressively," said Steven Wood, principal economist at Insight Economics LLC in Danville, Calif.